A comparison of the efficiency of electrocoagulation and alum NPs for tannic acid removal from aqueous solutions

This study aimed to optimize the removal of tannic acid (TA) from simulated wastewater by applying the electrocoagulation (EC) process and the alum nanoparticles (Al NPs) generated during the EC process, using the response surface method (RSM) methodology based on the central composite design (CCD). The structure and state of Al NPs were studied by X-ray diffraction analysis, field emission scanning electron microscopy, X-ray fluorescence (XRF), and Brunauer–Emmett–Teller analyses. We used four independent factors: current–voltage (20.83, 41.66, 62.49, 83.32, and 104.16 A/m²)/Al NPs dosage (0.1, 0.325, 0.55, 0.775, and 1 g/L), initial pH (5, 6, 7, 8, and 9/ 3, 5, 7, 9, and 11), initial TA concentration (10, 35, 60, 85, and 110 mg/L), and treatment time (10, 20, 30, 40, and 50 min). In addition, the total TA removal percentage was taken as a response variable. The analysis of the responses was performed using analysis of variance (ANOVA) as a statistical method. The quadratic model was proposed, and the ANOVA and model fitness were produced through RSM, with the coefficient of determination (R²) above 0.94 and 0.96 for all two responses representing the high importance of the suggested model. The EC process and the Al NPs removed TA with a maximum efficiency of 89.79% and 96.33%, respectively, in the optimal condition. The results indicated that the EC process and the Al NPs were effective and readily available methods for TA removal from aquatic environments.